Membrane Electrode Assembly and Organic Hydride Manufacturing Device

ABSTRACT

There is provided a membrane electrode assembly and an organic hydride manufacturing device capable of obtaining higher energy efficiency even if manufacturing organic hydride in one step with a single device. A membrane electrode assembly in which a cathode catalyst layer and an anode catalyst layer are placed to sandwich a solid polymer electrolyte membrane, wherein the cathode catalyst layer includes catalytic metal which causes hydrogenation of unsaturated hydrocarbons to organic hydrides, and a carrier of the catalytic metal, and the carrier provides on its surface a functional group which decreases wettability of the unsaturated hydrocarbons.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent applicationJP 2011-221674 filed on Oct. 6, 2011 the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a membrane electrode assembly and anorganic hydride manufacturing device, for manufacturing organic hydrideelectrochemically.

2. Description of the Related Art

While global warming by carbon dioxide and the like is getting serious,hydrogen as an energy source responsible for the next generation insteadof fossil fuels receives attention. With hydrogen fuels, the onlyemission during fuel consumption is water, and due to no carbon dioxideemission, the environmental load is low. On the other hand, becausehydrogen is a gas at the ordinary temperature and normal pressure, thesystem of transporting, storing, and supplying it is an importantproblem.

Recently, an organic hydride system using hydrocarbon like ascyclohexane, methylcyclohexane and decalin is drawing attention as asuperior hydrogen storing system in safety, transportability, andstoring capacity. Since these hydrocarbons are liquid at ordinarytemperature, they are superior in transportability. For example,although toluene and methylcyclohexane are cyclic hydrocarbons havingthe same carbon number, while toluene is an unsaturated hydrocarbon inwhich the bonding between the hydrocarbons is a double bond,methylcyclohexane is a saturated hydrocarbon having no double bond.Methylcyclohexane is yielded by the hydrogenation of toluene, andtoluene is yielded by the dehydrogenation. Thus, utilizing thehydrogenation and the dehydrogenation of hydrocarbon allows the storageand the supply of hydrogen.

To manufacture organic hydride such as methylcyclohexane, firstly, it isneeded to manufacture hydrogen, and then react the hydrogen and tolueneon a catalyst. In other words, the current process is a two-stageprocess in which hydrogen is yielded in water-electrolyzer and the like,and hydrogen and toluene is reacted to yield organic hydride in thehydrogenation device.

Therefore, plural devices are needed toward manufacturing organichydride, and there occurs a problem called complication of the devices.Furthermore, since hydrogen is a gas until hydrogenation occurs, thereoccurs a problem on the storage and the transport. If the hydrogenmanufacturing device and the hydrogenation device are constructedadjacently, the above-mentioned problem will be solved; however, thereis an issue of costs of construction and operation, and the overallenergy efficiency is also decreased. Furthermore, since the increasingsize of the devices is needed, there is also a problem that theinstallation location is limited.

Contrary to the two-stage process, the technologies of manufacturingorganic hydride in one-stage with only one device has been proposed (forexample, Japanese Patent Laid-Open 2003-45449, Catalysis Today, 56, 307(2000)). They manufacture organic hydride electrochemically. Forexample, in Japanese Published Unexamined Application No. 2003-45449,organic hydride is manufactured by placing metallic catalysts on theboth sides of a hydrogen ion permeable electrolyte membrane,respectively, supplying water or steam on one side and unsaturatedhydrocarbon (s) on the other side, and causing the hydrogenation ofunsaturated hydrocarbon (s) to saturated hydrocarbon (s) (organichydride (s)) by hydrogen ion yielded by electrolysis of water or steam.Respective reaction formulae of anode and cathode in the case of usingtoluene as an unsaturated hydrocarbon are as follows.

H₂O→2H⁺+(½)O₂+2e ⁻  (1)

C₇H₈+6H⁺+6e ⁻→C₇H₁₄  (2)

SUMMARY OF THE INVENTION

With these methods of manufacturing organic hydride, however, it hasbeen difficult to obtain higher energy efficiency.

An object of the present invention is to provide a membrane electrodeassembly and an organic hydride manufacturing device capable ofobtaining higher energy efficiency even if manufacturing organic hydridein one step with a single device.

One embodiment for achieving the above-mentioned object is a membraneelectrode assembly in which a cathode catalyst layer which reducesunsaturated hydrocarbons and an anode catalyst layer which oxides waterare placed to sandwich a solid polymer electrolyte membrane which isproton conductive, wherein the cathode catalyst layer includes acatalytic metal which makes an organic hydride by reducing theunsaturated hydrocarbon, a carrier which supports the catalytic metal,and the solid polymer electrolyte membrane which is proton conductive;and a functional group which decreases wettability of the unsaturatedhydrocarbon is introduced onto a surface of the carrier.

In addition, it is an organic hydride manufacturing device including themembrane electrode assembly, a member supplying the unsaturatedhydrocarbon to the cathode catalyst layer, and a member supplying wateror steam to the anode catalyst layer.

Furthermore, it is an organic hydride manufacturing device including acathode catalyst layer, an anode catalyst layer, and a separator whichsupplies an unsaturated hydrocarbon to the cathode catalyst layer toremove organic hydride, and supplies H₂O to the anode catalyst layer toevacuate oxygen and water, wherein the cathode catalyst layer is placedon one surface of a solid polymer electrolyte membrane, and the anodecatalyst layer is placed on another surface of the solid polymerelectrolyte membrane, the cathode catalyst layer includes a catalyticmetal which makes an organic hydride by reducing the unsaturatedhydrocarbon, and a carrier which supports the catalytic metal, and thecarrier has on its surface a functional group which decreaseswettability of the unsaturated hydrocarbon.

According to the present invention, by introducing a functional groupwhich decreases wettability of the unsaturated hydrocarbon on thesurface of the carrier which supports the catalytic metal, it ispossible to provide a membrane electrode assembly and an organic hydridemanufacturing device capable of obtaining higher energy efficiency, evenif manufacturing organic hydride in one step with a single device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating one example of an organichydride manufacturing device with relation to an embodiment of thepresent invention;

FIGS. 2A to 2C are views illustrating a membrane electrode assembly withrelation to an embodiment of the present invention; 2A is a plan view,2B is a D-E cross-sectional view of the plan view, and 2C is an enlargedview of part F of the cross-sectional view;

FIGS. 3A to 3C are views illustrating a membrane electrode assembly of arelated art; 3A is a plan view, 3B is a D-E cross-sectional view of theplan view, and 3C is an enlarged view of part F of the cross-sectionalview;

FIG. 4 is a view illustrating one example of the relation betweencurrent density and applied voltage, in the organic hydridemanufacturing device with relation to First Example of the presentinvention;

FIG. 5 is a view illustrating one example of the relation betweenconversion rate and applied voltage, in the organic hydridemanufacturing device with relation to First Example of the presentinvention;

FIG. 6 is a view illustrating one example of the relation betweencurrent density and applied voltage, in the organic hydridemanufacturing device with relation to First Comparative Example;

FIG. 7 is a view illustrating one example of the relation betweenconversion rate and applied voltage; and

FIG. 8 is a view illustrating one example of current density andconversion rate, in the organic hydride manufacturing device withrelation to the first to the third examples of the present invention,and First Comparative Example.

DETAILED DESCRIPTION OF THE INVENTION

The inventors examined the reasons why higher energy efficiency was notobtainable when manufacturing organic hydride in one-stage with theconventional single device. As a result, they found that there was aproblem in wettability of unsaturated hydrocarbons such as toluene toelectrodes, as one of the reasons. The electrodes of a single organichydride manufacturing device in one-stage is formed of the layer inwhich a proton conductive electrolyte is mixed with catalyst, and calledas a catalytic layer. Of the catalytic layer, a catalyst includes acarrier supports metallic catalyst such as platinum. The condition likehaving higher electron conductivity, higher specific surface area toprevent coagulation of metallic catalyst such as platinum and to enhancethe dispensability, and the like are needed for the carrier, andcarbon-based material is used generally.

However, the wettability of unsaturated hydrocarbons such as toluene tocarbon-based material is very strong and easy to become wet. Forexample, activated carbon is the carbon-based material which has largespecific surface area, and it is known that toluene is adsorbed toactivated carbon. It was speculated that when the wettability ofunsaturated hydrocarbons such as toluene to a carrier carbon was strong,the unsaturated hydrocarbon was covered on the carbon surface of thecarrier, and absorbed or stagnated on the carbon surface to inhibit theconsecutive supply of unsaturated hydrocarbons to a catalyst. In thatcase, a catalyst which is not supplied with unsaturated hydrocarbons anddoes not contribute to reaction appears and the energy efficiencybecomes low. Therefore, when the carrier carbon was surface-reformed,and the wettability of unsaturated hydrocarbons such as toluene wasdecreased, it was found possible to prevent stagnating of unsaturatedhydrocarbons on the surface of a catalytic layer and to supplyunsaturated hydrocarbons to catalyst stably.

The present invention originated from the basis of the above-mentionedfindings, and is able to make surface reforming to introduce afunctional group such as a sulfonate group, a hydroxyl group, acarboxylate group and the like in a catalytic carrier in a membraneelectrode assembly and an organic hydride manufacturing device, formanufacturing organic hydride electrochemically, and is able to usecarbon, as a catalytic carrier, which has been decreased in wettabilityof unsaturated hydrocarbons such as toluene. In addition, the catalystwhich supports metallic catalyst on the carbon, and the catalyst inwhich a solid polymer electrolyte membrane which is proton conductive ismixed together properly have electrode structures which are formed bothsides of a solid polymer electrolyte membrane which is protonconductive. On the electrodes, by applying voltage between anode-cathodein the situation that water or steam is supplied onto the anode side andunsaturated hydrocarbons are supplied onto cathode side, it is possibleto cause electrolysis of water on the anode and hydrogenation ofunsaturated hydrocarbons on the cathode, followed by producing organichydride.

Embodiments according to the present invention will be described withfigures in detail.

One example of an organic hydride manufacturing device according to anembodiment of the present invention is shown in FIG. 1. An organichydride manufacturing device of the embodiment is made up by jointing ananode catalyst layer 13 on one surface of a solid polymer electrolytemembrane 12 and a cathode catalyst layer 14 on the other surface of thesolid polymer electrolyte membrane 12, and sandwiching integratedmembrane electrode assembly (MEA) with a gas diffusion layer 15 and aseparator 11 in which a groove as a channel for gas and the like isformed. In addition, a gasket 16 for gas seal is inserted between a pairof the separators 11.

The separator 11 has electroconductivity, and for its quality ofmaterial, dense graphite plates, carbon plates into which carbonmaterials such as graphite and carbon black are molded by resin, as wellas metallic materials with superior corrosion resistance such asstainless steel and titanium are desirable. In addition, noble metalplating for the surface of the separator 11 and applying highlycorrosion resistant and heat resistant electro-conductive paint andpreparing surface treatment are also desirable. A groove which becomes achannel of reactive gas or liquid on the surface opposite to an anodecatalyst layer 13 and a cathode catalyst layer 14 of the separator 11 isformed. Water or steam is supplied through the groove channel of theseparator 11 on the anode side. Water or steam flowing through thegroove channel is supplied via gas diffusion layer 15 to the anodecatalyst layer 13. In addition, unsaturated hydrocarbons are suppliedonto the separator 11 of the cathode side. Unsaturated hydrocarbonsflowing through the groove channel are supplied via gas diffusion layer15 to a cathode catalyst layer 14. As a method of supplying unsaturatedhydrocarbons, liquid unsaturated hydrocarbons may be supplied intact,and/or vaporous unsaturated hydrocarbons making He gas, N₂ gas and thelike as a carrier may be supplied.

A gas diffusion layer 15 is arranged to supply reactive substances (gasor liquid) supplied into the channel of the separator 11 in planes ofcatalyst layers, and uses a substrate having gas permeability such ascarbon paper or carbon cloth.

The gasket 16 has insulation quality, and has resistance to, especially,hydrogen, unsaturated hydrocarbons, or organic hydride, and may havequality of material which has its less permeability and of whichhermeticity can be maintained, including butyl rubber, Viton rubber,EPDM rubber (ethylene-propylene-diene rubber) and the like, for example.

When applying voltage between anode and cathode in the state ofsupplying water or steam at the anode side and toluene as an unsaturatedhydrocarbon at the cathode side, electrolysis of water according to theformula (1) occurs. Proton yielded by electrolysis according to theformula (1) transfers via a solid polymer electrolyte membrane 12 to acathode catalyst layer 14, and in the cathode catalyst layer,hydrogenation according to the formula (2) occurs and methylcyclohexanewhich is organic hydride yields.

H₂O→2H⁺+(½)O₂+2e ⁻  (1)

C₇H₈+6H⁺+6e ⁻→C₇H₁₄  (2)

An organic hydride device of the present embodiment makes hydrogenationof unsaturated hydrocarbons electrochemically to yield organic hydride.

FIGS. 2A to 2C show electrode parts of an organic hydride manufacturingdevice according to the embodiment. FIGS. 2A to 2C show a plan view ofMEA where a cathode catalyst layer 22 or an anode catalyst layer 23 oneach side of a solid polymer electrolyte membrane is formed seen fromthe cathode side, a D-E cross-sectional view of the plan view, and anenlarged view of part F of the cross-sectional view, respectively.

As illustrated in the D-E cross-sectional view, the cathode and theanode are formed as dense catalyst layers on and below a solid polymerelectrolyte membrane 21. As the cathode catalyst layer 22 is illustratedon the enlarged view, catalytic metal 24 is supported on the carbon(carrier) 25 which is a catalytic carrier. The surface treatment isprepared on the carbon 25, and functional groups 27 are introduced.Thus, unsaturated hydrocarbons such as toluene are difficult to wet tothe catalyst, and unsaturated hydrocarbons are supplied stably to thecatalyst, without covering the catalytic layer surface with unsaturatedhydrocarbons and stagnating. In addition, fugacity of organic hydrideyielded by hydrogenation becomes also higher. Furthermore, the number 28denotes unsaturated hydrocarbons or organic hydride.

The carbons 25 are adhered each other with a solid polymer electrolyte26. The catalytic metal 24 has a network configuration linked via carbon25 together, and forms a path for electron required for the reaction ofthe formula (2). In addition, a solid polymer electrolyte 26 has alinking network configuration as well, and forms a path for protonrequired for the reaction of the formula (2).

Electrode reaction is conducted at the three-phase interface where thecatalytic metal 24 on the carbons 25, a solid polymer electrolyte, andthe reactant unsaturated hydrocarbons contact. In the electrode of theembodiment, a path for proton is formed by a solid polymer electrolyte26, so that the three-phase interface is formed even in the catalyticmetal 24 which does not contact directly the solid polymer electrolytemembrane 21, then there is provided a configuration in which manymetallic catalysts are able to contribute to the electrode reaction,provided that the solid polymer electrolyte membrane 21 provides a solidpolymer electrolyte and it is desirable but not essential for a cathodecatalyst layer to comprise solid polymer electrolytes 26.

An electrode part of an organic hydride manufacturing device of arelated art is shown in FIGS. 3A to 3C. FIGS. 3A to 3C show a plan viewof an MEA where a cathode catalyst layer 32 and an anode catalyst layerare formed on each side of a solid polymer electrolyte membrane 31, partD-part E cross-sectional view of the plan view, and an enlarged view ofpart F of the cross-sectional view, respectively. On the electrodes inthe FIGS. 3A to 3C, unsaturated hydrocarbons cover on the carbon surfaceof the carrier, and absorb or stagnate on the carbon surface, so thatunsaturated hydrocarbons are not supplied, catalysts not contributing tothe reaction are generated, and energy efficiency becomes lower.Furthermore, the number 34 denotes catalytic metal, the number 35denotes carbon carrier, and the number 36 denotes unsaturatedhydrocarbons or organic hydride.

The carbon 25, which is a catalytic carrier of the embodiment, ischaracterized in that the functional groups 27 are introduced by surfacereforming. Hereby, unsaturated hydrocarbons become difficult to wet,stagnation of unsaturated hydrocarbons on the surface of a cathodecatalyst layer 22 is prevented, and the supply of unsaturatedhydrocarbons to the cathode catalyst layer 22 is not inhibited.

Anything is acceptable for the functional groups 27 which are introducedon the carbon surface as long as they decrease wettability ofunsaturated hydrocarbons such as toluene and increase oil repellency.For example, they include a sulfonate group, a phosphonate group, ahydroxyl group, a sulfomethyl group, a carboxyl group, a carbonyl group,a carboxylate group and the like. At least one of these may be included,and especially a sulfonate group is practically suitable.

As the carrier 25, anything is acceptable as long as it iselectron-conductive carbon. For example, it includes furnace black andchannel black, acetylene black, amorphous black, carbon nanotube, carbonnanohorn, carbon black, activated carbon, graphite and the like. Thesecan be used alone or by mixture.

As a method of surface-treating of carbon to introduce functionalgroups, for example, it is possible to treat carbon with sulfuric gas,fuming sulfuric acid, sulfuric acid and the like to introduce sulfonategroups. In addition, it is possible to treat carbon with sodium sulfite,sodium bisulfite, aqueous formalin solution, paraformaldehyde and thelike to introduce a sulfomethyl group. Moreover, it can be considered toirradiate oxygen plasma for the introduction of hydroxyl groups.

On the other hand, a catalytic material causing hydrogenation is used asthe catalytic metal 24 used in the present embodiment, metals such asNi, Pd, Pt, Rh, Ir, Re, Ru, Mo, W, V, Os, Cr, Co, Fe and the like aswell as their alloy catalysts, for example, are possible to use, andespecially, Pt (platinum), ruthenium (Ru), rhodium (Rh), palladium (Pa),iridium (Ir), molybdenum (Mo), rhenium (Re), wolfram (W) and their alloyare practically suitable. It is preferable to micronized hydrogenationcatalysts, for cost reduction by the decrease of catalytic metals, andan increased reaction surface area.

In addition, as a method of supporting the catalytic metal 24 on thecarrier carbon 25, there are coprecipitation, thermal decomposition,electroless plating and the like, and have no particular limitation.

The MEA of the embodiment can be prepared by the following method.Firstly, a cathode catalyst paste to which a catalyst with the catalyticmetal 24 supported by the surface-treated carbon 25, a solid polymerelectrolyte, and a solvent which dissolved a solid polymer electrolyte,is added to mix thoroughly, and an anode catalyst paste where platinumblack, a solid polymer electrolyte, and a solvent which dissolved asolid polymer electrolyte are added to mix thoroughly are prepared.Those pastes are sprayed onto release film such as polyfluoroethylene(PTFE) film, with spray-dry method and the like, respectively, and driedat 80° C. to evaporate the solvent to form cathode and anode catalystlayers. Next, those cathode and anode catalyst layers are joined by hotpress method with sandwiching the solid polymer electrolyte membrane 21in the middle, and it is possible to prepare MEA of the embodiment bypeeling off the release film (PTFE).

In addition, as another example of MEA preparation of the presentembodiment, it is also possible to prepare it by spraying a cathodecatalyst paste in which a catalyst with the catalytic metal 24 supportedby the surface-treated carbon 25, a solid polymer electrolyte, and asolvent which dissolves a solid polymer electrolyte are added to theabove-mentioned surface-treated carbon 25 and mixed thoroughly, andanode catalyst paste in which platinum black, a solid polymerelectrolyte, and a solvent which dissolves a solid polymer electrolyte,to the solid polymer electrolyte membrane 21 directly with spray-drymethod and the like.

As polymer electrolytes which compose the solid polymer electrolytemembrane 21, perfluorocarbon sulfonate, or materials which have doped orbound chemically and fixed proton donor such as sulfonate groups,phosphonate groups and carboxyl groups to polystyrene, polyether ketone,polyetherether ketone, polysulfone, polyethersulfone or the otherengineering plastic materials, can be used. In addition, by transformingthe above-mentioned materials to cross-linked structure or fluorinatingit partially, the material stability can be enhanced.

For a solid polymer electrolyte contained in a catalytic layer, apolymer material which shows proton conductivity is used, and examplesinclude sulfonated or alkylene-sulfonated fluorine-based polymer andpolystyrenes which are represented by perfluorocarbon-based sulfonateresin and polyperfluorostyrene-based sulfonate resin. Further, thematerials in which proton donor is introduced to polysulfonespolyethersulfones, polyetherethersulfones, polyetherether ketones, orhydrocarbon-based polymer are included. In addition, compositeelectrolyte of polymer material of the embodiment and metal oxidehydrates can be used.

As an unsaturated hydrocarbon, aromatic hydrocarbon can be used, and forexample either of benzene, toluene, xylene, mesitylene, naphthalene,methylnaphthalene, anthracene, biphenyl, phenanthroline and their alkylsubstitutes, or a multi-mixture can be used. Hydrogen is added to adouble bond of these carbons so that hydrogen can be stored.

In the following, the present invention will be described with examplesin detail. However, the present invention is not limited to examplesmentioned below.

First Example

As a catalyst, a catalyst where 30 wt % of Pt particulates was dispersedand supported on carbon black was used. Firstly, 100 g of this catalystwas preheated for one hour at 105° C. Subsequently, sulfur trioxideheated to 100° C. was transferred at 12 vol. % of concentration to dryair, and reacted with the catalyst. Reaction time was two hours.Subsequently, it was cooled, the catalyst was submitted to ion exchangedwater, stirred and filtrated, and washed with ion exchanged water untilpH of the filtrate became constant.

When the infrared absorption spectrum was measured to the obtainedcatalyst, the peaks were observed at 620 cm⁻¹, 1037 cm⁻¹ and 1225 cm⁻¹.This was considered as the peak based on the sulfonate group —SO₃H, andit was confirmed that the sulfonate group was introduced on the surfaceof the carbon black which was a carrier. The equivalent of theintroduced sulfonate group was 1.8 milliequivalent/g dry carbon carrier.

The above-obtained catalyst was used as a cathode catalyst, and MEA, theconfiguration of which was shown in FIG. 2, was prepared. Nafion(manufactured by DuPont) was used for an electrolyte membrane. A cathodecatalyst layer 22 was formed by applying catalyst slurry on Nafiondirectly with a spray coater. The cathode catalyst layer 22 was appliedon Nafion in the following order.

Firstly, Nafion was put on a hotplate as a substrate, and was fixed bysuction. The temperature of the hot plate was 50° C. Next, a mask wasput on it, and cathode catalyst slurry was sprayed with a spray coater(manufactured by Nordson). The mixture of the catalyst prepared in theexample and water, 5% (wt) Nafion solution and 221 solution (thesolution of 1-propanol:2-propanol:water=2:2:1) was used in the weightratio of 2:1.2:5.4:10.6. Spraying condition was 0.01 MPa of hydraulicpressure, 0.15 MPa of swirl pressure, 0.15 MPa of atomization pressure,60 mm of gun/substrate distance and 50° C. of substrate temperature. Theamount of the cathode catalyst was 0.4 mg Pt·cm⁻².

A cathode catalyst layer 22 was formed on a Nafion surface, followed byforming an anode catalyst layer 23 on the opposite surface. The anodecatalyst layer 23 was formed by transferal. Firstly, anode catalystslurry was prepared. A mixture of platinum black HiSPEC1000(manufactured by Johnson Matthey), 5% (wt) Nafion solution and 221solution was used in the weight ratio of 1:1.11:2.22. It was applied onTeflon (registered trademark) sheet by an applicator. The anode catalystlayer which was applied on Teflon (registered trademark) sheet wasformed on the Nafion surface with heat transfer printing by hot press(SA-401-M manufactured by Tester Sangyo). The pressure of hot press was37.2 kgf·cm², the temperature of hot press was 120° C., and hot presstime was two minutes. The amount of anode catalyst was 4.8 mg Pt·cm⁻².

The prepared MEA was incorporated into the device of manufacturingorganic hydride in FIG. 1. Toluene was used as an unsaturatedhydrocarbon. In the state that toluene was supplied to cathode in 10cc/min and purified water was supplied to the anode in 5 cc/min, voltagewas applied between the anode and the cathode. It was conducted at 80°C. of the cell temperature. The value of the current to the appliedvoltage is shown in FIG. 4. When applying 1.6 V or above of voltage, acurrent flowed and the reaction proceeded. As the voltage was increasedto 2.2 V, the current increased and the reaction proceeded. When thecathode emission gas was analyzed by gas chromatography, toluene andmethylcyclohexane were detected. Hereby, it was confirmed thatmethylcyclohexane was yielded by hydrogenation of toluene. FIG. 5 showsthe conversion ratio of toluene to methylcyclohexane, calculated fromthe peak intensity of gas chromatography. As the voltage was increased,the conversion ratio was improved, and the maximum value in thiscondition was 55% when applying 2.2 V.

As mentioned above, according to the example, a membrane electrodeassembly and an organic hydride manufacturing device capable ofobtaining higher energy efficiency can be provided by introducingfunctional groups, which decrease wettability of unsaturatedhydrocarbons, on the carrier surface of a catalyst even if organichydride is manufactured with a single device in one step.

First Comparative Example

As a catalyst, a catalyst was used where 30% (wt) of Pt particulates wasdispersed and supported on carbon black for which surface treatment tointroduce functional groups was not conducted. This catalyst was used ascathode catalyst to prepare MEA. The preparation was conducted in themethod and condition for the preparation similar to those of FirstExample.

The prepared MEA was incorporated into the device of manufacturingorganic hydride in FIG. 1, and the experiment of hydrogenation oftoluene in similar condition to First Example was conducted. FIG. 6shows a value of the current to the applied voltage. The value of thecurrent was smaller than that of First Example. This is considered to bebecause the wettability of toluene to carbon was strong, toluene wasstagnated on the carbon surface, and the supply of toluene onto catalystwas prevented. Furthermore, when the occurred gas flow rate wasmeasured, the gas flow rate was increased in First Comparative Examplein comparison with First Example. This is considered to be because, onthe catalyst where toluene is not supplied, hydrogen generation occursby the reaction according to the following formula (3)

2H⁺+2e ⁻→H₂  (3)

FIG. 7 shows the conversion ratio of toluene to methylcyclohexane. Themaximum value in this condition was 30% when applying 2.2 V. It was alower conversion ratio than that of First Example. This is considered tobe because not only hydrogenation but also hydrogen generation occurssimultaneously. The energy efficiency of organic hydride production canbe lower to that extent.

As mentioned above, even if there is a similar configuration to FirstExample except for the introduction of functional groups, a membraneelectrode assembly and an organic hydride manufacturing device whichhave higher energy efficiency cannot be obtained.

Second Embodiment

As a catalyst, a catalyst where 30% (wt) of Pt particulates wasdispersed and supported on carbon black was used. 10 g of this catalystand 15 g of anhydrous aluminum chloride (AlCl₃) were mixed andthiophosphoryl chloride (PSCl₃) was added gradually. The temperature ofPSCl₃ was fixed at 35° C. and 54 mL was added slowly. Subsequently, itwas kept at 75° C. for 45 minutes. After cooling, 50 mL of chloroformwas added and filtrated. After washing with diethyl ether thoroughly,200 mL of ion-exchanged water was added and refluxed for 20 hours. Whenthe infrared absorption spectrum of the obtained catalyst was measured,the peaks were observed at 1000 to 1120 cm⁻¹ and 840 to 910 cm⁻¹. Thiswas considered as the peak based on phosphonate, and it was confirmedthat phosphonate groups were introduced onto the surface of the carriercarbon black. The equivalent of the introduced phosphonate groups was1.8 milliequivalent/g dry carbon carrier.

The prepared catalyst was used for cathode catalyst to prepare an MEA.The preparation was conducted in the method and condition for thepreparation similar to those of First Example.

The prepared MEA was incorporated into the device of manufacturingorganic hydride in FIG. 1, and the experiment of hydrogenation oftoluene was conducted in the similar condition to First Example. Theresult is shown in FIG. 8. FIG. 8 is the current density and theconversion ratio when applying 2.2 V between the anode and the cathode.Compared to First Comparative Example in which surface treatment ofcarrier carbon was not conducted, it resulted in an increase of both thecurrent density and the conversion ratio, and the effect of introducingphosphonate groups onto the carbon surface was found.

As mentioned above, according to the example, a membrane electrodeassembly and an organic hydride manufacturing device capable ofobtaining higher energy efficiency can be provided by introducingfunctional groups, which decrease wettability of unsaturatedhydrocarbons, on the carrier surface of catalyst even if organic hydrideis manufactured with a single device in one step.

Third Example

As a catalyst, a catalyst where 30 wt % of Pt particulates was dispersedand supported on carbon black was used. Oxygen plasma was irradiated tothis catalyst. The device to use for irradiation was a plasma device,Cat. No. PDC210 manufactured by Yamato Glass, and the pressure in thechamber before introducing oxygen was 0.1 Torr or lower, and thepressure after introducing oxygen was 0.5 Torr. The output of a highfrequency power source of the device was 100 W, and plasma irradiationtime was 150 seconds. When infrared absorption spectrum of the yieldedcatalyst was measured, a broad peak was observed at 3000 to 3600 cm⁻¹.This was considered as the peak based on the hydroxyl group —OH, and itwas confirmed that the hydroxyl group was introduced on the surface ofPt supported carbon black.

The prepared catalyst was used for cathode catalyst to prepare an MEA.The preparation was conducted in the method and condition for thepreparation similar to those of First Example.

The prepared MEA was incorporated into the device of manufacturingorganic hydride in FIG. 1, and the experiment of hydrogenation oftoluene in the similar condition to First Example. The result is shownin FIG. 8. Compared to First Comparative Example in which surfacetreatment of carrier carbon was not conducted, it resulted in anincrease of both the current density and the conversion ratio, and theeffect of introducing hydroxyl groups onto the carbon surface was found.

As mentioned above, according to the example, a membrane electrodeassembly and an organic hydride manufacturing device capable ofobtaining higher energy efficiency can be provided by introducingfunctional groups, which decrease wettability of unsaturatedhydrocarbons, on the carrier surface of catalyst even if organic hydrideis manufactured with a single device in one step.

However, the present invention is not limited the above-mentionedexamples, and various modifications are included. For example, theabove-mentioned examples are explained in detail to explain the presentinvention simply, and not necessarily limited to that provides all theconfigurations explained. In addition, it is also possible to substitutepart of the configuration of one example with configuration of anotherexample, and moreover, it is also possible to add, to the configurationof one example, the configuration of another example. Furthermore, forpart of the configuration of each example, it is possible to makeaddition, deletion, or substitution of another configuration.

What is claimed is:
 1. A membrane electrode assembly in which a cathodecatalyst layer which reduces an unsaturated hydrocarbon and an anodecatalyst layer which oxides water are placed to sandwich a solid polymerelectrolyte membrane which is proton conductive, wherein the cathodecatalyst layer includes a catalytic metal which causes hydrogenation ofa unsaturated hydrocarbon to organic hydride, a carrier which supportsthe catalytic metal, and the solid polymer electrolyte membrane which isproton conductive; and a functional group which decreases wettability ofthe unsaturated hydrocarbons is introduced onto a surface of thecarrier.
 2. An organic hydride manufacturing device, comprising themembrane electrode assembly according to claim 1, a member supplying theunsaturated hydrocarbon to the cathode catalyst layer, and a membersupplying water or steam to the anode catalyst layer.
 3. The membraneelectrode assembly according to claim 1, wherein the functional groupincludes at least one of a sulfonate group, a phosphonate group, ahydroxyl group, a sulfomethyl group, a carboxyl group, a carbonyl group,and a carboxylate group.
 4. The membrane electrode assembly according toclaim 1, wherein the catalytic metal consists of platinum, ruthenium,rhodium, palladium, iridium, molybdenum, rhenium, wolfram, and an alloyincluding at least some of these.
 5. The membrane electrode assemblyaccording to claim 1, wherein the unsaturated hydrocarbon is benzene,toluene, xylene, mesitylene, naphthalene, methylnaphthalene, oranthracene.
 6. The organic hydride manufacturing device according toclaim 2, wherein the unsaturated hydrocarbon is benzene, toluene,xylene, mesitylene, naphthalene, methylnaphthalene, or anthracene.
 7. Anorganic hydride manufacturing device comprising a cathode catalystlayer, an anode catalyst layer, and a separator which supplies anunsaturated hydrocarbon to the cathode catalyst layer to remove organichydride, and supplies H₂O to the anode catalyst layer to evacuate oxygenand water, wherein the cathode catalyst layer is placed on one surfaceof a solid polymer electrolyte membrane, and the anode catalyst layer isplaced on another surface of the solid polymer electrolyte membrane, thecathode catalyst layer includes a catalytic metal which causeshydrogenation of an unsaturated hydrocarbon to the organic hydride, anda carrier which supports the catalytic metal, and the carrier has on itssurface a functional group which decreases wettability of theunsaturated hydrocarbon.
 8. The organic hydride manufacturing deviceaccording to claim 7, wherein hydrogen is supplied from the anodecatalyst layer to the cathode catalyst layer.
 9. The organic hydridemanufacturing device according to claim 7, wherein the carrier iselectron-conductive carbon.
 10. The organic hydride manufacturing deviceaccording to claim 7, wherein the functional group is a sulfonate group.11. The organic hydride manufacturing device according to claim 7,wherein the separator has electroconductivity as well as a channelgroove through which unsaturated hydrocarbons and H₂O flow.
 12. Theorganic hydride manufacturing device according to claim 7, whereinsupply of unsaturated hydrocarbons onto the cathode catalyst layer andsupply of H₂O onto the anode catalyst layer are feasible via a diffusionlayer.
 13. The organic hydride manufacturing device according to claim12, wherein the diffusion layer is carbon paper or carbon cloth.
 14. Theorganic hydride manufacturing device according to claim 7, wherein thecathode catalyst layer includes a solid polymer electrolyte.